Digital Rights Management (DRM) is a category of technologies that restrict how digital content can be played, copied, or shared after it's delivered to a viewer. In the context of video, DRM means encrypting the stream so that it can only be decoded by an authorised player, on an authorised device, for an authorised viewer. The dominant consumer DRM systems are Google Widevine, Apple FairPlay, and Microsoft PlayReady; most professional video hosts support all three.
I recommend DRM in a narrow set of cases — paid courses, paywalled investigative journalism, pre-release media, and licensed third-party content where the licensing terms require it. For most marketing and educational video, DRM is overkill. A determined person with a screen recorder can capture anything they can watch, so DRM doesn't stop the most motivated piracy; what it does is raise the friction enough to deter casual download tools and browser extensions.
The more useful protection for most clients is dynamic watermarking — overlaying the viewer's email address, IP, or session ID on top of the video in real time. It doesn't prevent recording, but it makes leaked recordings traceable, which changes the incentive for the viewer.
On the implementation side, the practical choice is between a host that offers DRM as a feature (Vimeo OTT, Mux, Cloudflare Stream, Brightcove) and rolling your own with AWS Elemental or a similar pipeline. The hosted route costs more per view but removes the operational burden of key management, license servers, and certificate renewals — all of which can fail in ways that break playback for paying viewers, which is worse than the piracy you were trying to prevent.